Vibration isolation member

ABSTRACT

A vibration isolation member comprising an inner member comprising an outer periphery having a first dimension; an outer member comprising a base and a shroud that extends away from the base, the shroud adapted to overlay the inner member, said shroud defining an inner periphery having a second dimension, the second dimension being less than the first dimension; and a resilient member constrained between the shroud and the inner member, whereby the vibration isolation member provides iso-elastic dynamic stiffness and an interference between the inner and outer members in the event of a failure of the resilient member.

FIELD OF THE INVENTION

The invention relates to a vibration isolation member and moreparticularly the invention relates to a vibration isolation member thatprovides substantially equal dynamic stiffness in radial and axialdirections and comprises an outer member with an inner periphery, aninner member with an outer periphery and a resilient member joining theinner and outer members wherein the dimensions of the inner and outerperipheries provide for an interference therebetween in the event of afailure of the elastomer.

BACKGROUND OF THE INVENTION

Vibration isolation members are frequently used in aircraft interiorapplications to reduce the vibration and noise exposure to delicate andsensitive instrumentation and also to passengers in the aircraft cabin.In aircraft applications the vibration isolation members must providethe requisite vibration reduction with a minimum size and weightvibration isolation member.

One means for effectively reducing such exposure to noise and vibrationis to use a vibration isolation member that has iso-elastic stiffnessproperties. A vibration member that is iso-elastic has equal stiffnessin the axial and radial directions. Iso-elastic stiffness permits thevibration isolator to provide dependable performance in any orientationand maximize vibration reduction for a given installation. A vibrationisolation member that does not provide such iso-elastic stiffnessproperties will transmit vibration more efficiently in one or moredirections, compared to an iso-elastic vibration member having the sameminimum stiffness.

Additionally, it is desirable to include a mount fail-safe feature thatprevents the mount from separating in the event the mount fails underloading. Several prior art mounts provide fail safe features thatfunction in a single axial direction however, such prior art mountstypically do not have two fail safe paths. Moreover, in vibrationisolation members that comprise iso-elastic members, the membersfrequently do not have a fail-safe or interference path that is definedby the components that comprise the mount. Rather the fail-safe featureis produced by adding washers or other discrete mechanical members tothe member. The additional components required to provide a fail safefeature in an iso-elastic vibration isolation member add weight andincrease the volume required to house the member in the aircraft.

The foregoing illustrates limitations known to exist in present devicesand methods. Thus, it is apparent that it would be advantageous toprovide a vibration isolator that provides iso-elastic stiffness incombination with fail safe feature and thereby solves one or more of theshortcomings of present isolation devices and methods. Accordingly, asuitable vibration isolation member is provided including features morefully disclosed hereinafter.

SUMMARY OF THE INVENTION

In one aspect of the present invention this is accomplished by providinga vibration isolation member that provides iso-elastic stiffness and atleast one fail-safe feature.

More specifically the vibration isolation member of the presentinvention comprises an inner member comprising an outer periphery havinga first dimension; an outer member comprising a base and a shroud thatextends away from the base, the shroud adapted to overlay the innermember, said shroud defining an inner periphery having a seconddimension, the second dimension being less than the first dimension; anda resilient member constrained between the shroud and the inner member,whereby the vibration isolation member provides iso-elastic stiffnessand an interference between the inner and outer members in the event ofa failure of the resilient member.

The inner member is unitary and is comprised of a stem and a seat wherethe seat includes a first surface, a second surface spaced from thefirst surface and a third surface that joins the first and secondsurfaces. The third surface is oriented at an angle relative to thefirst surface. The seat has a frustoconical configuration.

The outer member shroud may comprise a single segment or may comprise afirst segment, a second segment and a third segment, the second segmentjoining the first and third segments. The outer member first segment isoriented substantially axially, the third segment is orientedsubstantially radially and the second segment is oriented at an anglerelative to the first and second segments. The third surface of the seatis substantially parallel to the second segment of the shroud.

The foregoing and other aspects will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of the vibration isolation member of thepresent invention.

FIG. 2 is a top view of the vibration isolation member of FIG. 1.

FIG. 3 is a longitudinal sectional view taken along line 3-3 of FIG. 2.

FIG. 4 is a longitudinal sectional view like the sectional view of FIG.3 illustrating a second embodiment vibration isolation member of thepresent invention.

FIG. 5 is a longitudinal sectional view like the sectional view of FIG.3 illustrating third embodiment vibration isolation member of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning to the drawing Figures wherein like parts are referred to by thesame numbers in the Figures, the first embodiment vibration isolationmember 10 of the present invention is disclosed in FIGS. 1, 2 and 3.

Generally, vibration isolation member 10 comprises an inner member 12,an outer member 14 and a resilient member 16 that joins the inner andouter members. The resilient member is constrained between the inner andouter members. The inner and outer members 12 and 14 are relativelyrigid. The vibration isolation member 10 is made from a conventionalmolding process well known to those skilled in the art and during themolding process the resilient member is bonded to the inner and outermembers. The resilient member 16 may be comprised of any suitablematerial however for purposes of the preferred embodiment of theinvention the resilient member is comprised of a silicone or a syntheticrubber.

As shown in the sectional view of FIG. 3, the isolator is adapted to beconnected between a support structure 18 such as an aircraft frame forexample, and a suspended body 20 which may be an interior aircraftinstrument or trim panel. The isolator 10 of the present inventionreduces the transmission of vibratory disturbances, which may be in theform of acoustic noise, between the support structure 18 and thesuspended body 20. The isolator also limits heat transfer between body20 and structure 18. Also shown in FIG. 3, the isolation member isjoined to the suspended body 20 by conventional fastener 22 that extendsbetween the body 20 and inner member 12; and is joined to the supportstructure 18 by fasteners 24 a, 24 b that extend through the outermember 14. The fasteners may be comprised of any suitable fastener wellknown to those skilled in the art including, but not limited to screwsor quick-connect fasteners. By these connections, the outer member 14remains substantially stationary during use and the inner member 12 maybe displaced in radial and axial directions represented by respectivedirectional arrows 25 and 26.

The relatively rigid inner member 12 is unitary and comprises an axiallyextending cylindrical stem 30 and frustoconical seat 32. As shown inFIG. 3, the seat includes first and second faces 34 and 36 joined byangled surface 38 that extends outwardly from face 34 to face 36. Thesurface 38 may extend at any suitable angle, Θ relative to face 34. Forpurposes of describing the preferred embodiment of the invention, theangle may be about 55°. The stem is made integral with the seat 32 atface 34 and the free end of the stem extends outwardly from the openingin the outer member 14 defined by inner periphery 62. Faces 34 and 36are circular, planar members that join the surface 38 at respectiveouter edges. The inner member includes an axially extending bore 40 thatextends through the stem and seat and is adapted to receive fastener 22previously described above. The seat defines an outer periphery 42 thatcomprises a diameter, D′. The extent of the inner member outer periphery42 is also represented in dashed font in FIG. 2. As shown in FIG. 3,when the member 10 is installed the seat is located proximate thesupport member 18. Additionally, as shown in FIG. 3, the surface 36 islocated a distance away from the support structure 18 to allow fordisplacement of inner member 12 when the isolation member 10 experiencesa vibratory disturbance.

The relatively rigid outer member 14 is unitary and comprises asubstantially planar flange or base 50 with bores 52 a and 52 b that areadapted to receive fasteners 24 a and 24 b as described hereinabove. Thebase 50 is made integral with an annular shroud 54 that overlays seat32. The shroud comprises a first segment 56 that extends in the axialdirection defined by arrow 26, a second segment 58 that extendssubstantially parallel to surface 38, and a third segment 60 thatextends in the radial direction defined by arrow 25. The second segment58 joins the first and third segments 56 and 60. See FIG. 3. Althoughthe second segment is shown at an orientation that is substantiallyparallel to surface 38 it should be understood that although such aparallel configuration is preferred the second segment could be orientedat any relative angle and do not have to be parallel.

Third segment 60 terminates at inner periphery 62 that defines diameter,D″. As shown in FIGS. 2 and 3, the outer periphery 42 has a diameter D′that has a greater radial dimension than inner periphery 62 diameter,D″. In the event that resilient section fails, and the seat is displacedaxially toward panel 20, an interference or fail-safe load path would becreated between the seat and the segment 60 preventing furtherdisplacement of seat outward from the outer member. Thus the innermember would be captured by the outer member. As shown most clearly inthe sectional view of FIG. 3, to ensure that the desired interference isproduced between the seat and shroud, the inner periphery 62 mustterminate radially inwardly from the outer periphery 42.

During molding, resilient member 16 is bonded to the surface 38 and alsoto the inner surface of second segment 58. Additionally, the moldingprocess produces relatively thin skin segments bonded along the innersurface of third segment 60 and inner periphery 62, stem 30 and surface34, outer periphery 42 and along portions of the inner surfaces offlange 50 and first segment 56. Apart from the skins, the main portionof the resilient member 16 has a substantially trapezoidal crosssection.

The vibration isolation member 10 of the present invention providesiso-elastic stiffness. The term “iso-elastic” means that the isolationmember 10 has substantially the same stiffness in the axial and radialdirections for any applied load. Because the resilient member 16 isconstrained between the inner member 12 and outer member 14 theresilient member 16 experiences combined shear loads and loads in eithertension or compression regardless of the direction and magnitude of theload applied to the vibration isolation member 10.

The vibration isolation member 10 of the present invention provides adouble fail safe feature that captures the inner member and maintains itin the chamber 80 defined by the outer member and the support structure18. Failure of the elastomer member 16 or failure of the bonds betweenmember 16 and either inner member 12 or outer member 14 will not permitthe inner member to relocate outside of the outer member. The innermember is captured by either the structural panel 18 or by theinterference between the seat and segment 60 as described hereinabove.Therefore, in order for the inner member seat to become displaced fromthe chamber 80, failure of the inner member, outer member fasteners orstructural member must occur in addition to the resilient memberfailure. Additionally, in the event the resilient member 16 fails theseat will not be displaced out of chamber 80. The suspended body 20 willengage the rigid outer member while the seat will interfere with theinner member. Additionally, the structural member will impede additionalaxial displacement of the seat towards member 20. In this way, the mountof the present invention provides double fail-safe feature incombination with its iso-elastic stiffness.

A second preferred embodiment vibration isolation member 70 is shown inFIG. 4. The alternate embodiment mount 70 includes relatively rigidinner member 72 comprises stem 30 and seat 32 which defines angledsurface 38. The stem 30, seat 32 and surface 38 as well as the othercomponents and features are the same as those described hereinabove inconjunction with first embodiment vibration isolation member 10. In thesecond embodiment mount 70, the stem 30 and seat 32 may be made directlyintegral. The inner member 72 does not include surface 34 joining thestem and seat. The second embodiment member 70 includes the doublefail-safe feature and also includes an iso-elastic stiffness.

A third preferred embodiment vibration isolation member 75 isillustrated in FIG. 5. The alternate embodiment mount 75 includesrelatively rigid outer member 76 with shroud 78. As shown in FIG. 5, theshroud member is comprised of a hollow cone with a wall comprised of asingle angled segment, that terminates at an inner periphery 62. Asdescribed in conjunction with first embodiment isolation member 10, theinner periphery 62 has a diameter D″ that is less than the diameter D′of the outer periphery 42 of the seat 32. The other components andfeatures of member 75 are the same as those described hereinabove inconjunction with first embodiment vibration isolation member 10. Thethird embodiment member 70 includes the double fail-safe feature andalso includes an isoelastic stiffness.

It should be understood the use of outer member 76 and inner member 72are not limited to the isolation members shown in their respectiveembodiments but rather, outer member 76 may be combined with innermember 72 if desired.

While I have illustrated and described a preferred embodiment of myinvention, it is understood that this is capable of modification, and Itherefore do not wish to be limited to the precise details set forth,but desire to avail myself of such changes and alterations as fallwithin the purview of the following claims.

1. A single resilient member iso-elastic vibration isolation membercomprising: (a) an inner member for attachment to a suspended body, saidinner member comprising a frustoconical seat having an angled surfaceand an outer periphery diameter D′; (b) an outer member for attachmentto a planar support structure, said outer member comprising a planarbase defining a base plane and a shroud that extends away from theplanar base and said base plane, the shroud extending to overlay theinner member outer periphery diameter D′, said shroud having an angledsegment with an inner surface, said angled segment inner surfaceoriented substantially parallel to said angled surface of saidfrustoconical seat, said shroud defining an inner periphery diameter D″,said inner periphery diameter D″ less than said outer periphery diameterD′, said inner member not extending through said outer member baseplane; and (c) consisting essentially of a single sole resilient memberconstrained between the shroud angled segment inner surface and theinner member frustoconical seat angled surface, said single resilientmember having a cross section, said single resilient member bonded tosaid shroud angled segment inner surface and said inner memberfrustoconical seat angled surface, wherein said single resilient memberbonded to said shroud angled segment inner surface and said inner memberfrustoconical seat angled surface provides for iso-elastic displacementof said inner member in a radial direction and in an axial directionfrom said outer member with said frustoconical seat outer peripherydiameter D′ providing an interference with said shroud inner peripherydiameter D″ to prevent a seperation of the vibration isolation member inthe event of a failure of said single resilient member, wherein saidsingle sole resilient member is the sole resilient member providing forisolation between the suspended body and the support structure with saidiso-elastic vibration isolation member providing a substantially equaldynamic stiffness in the radial direction and in the axial direction foran applied load between the suspended body and the support structure. 2.The vibration isolation member of claim 1 wherein the inner member iscomprised of a stem.
 3. The vibration isolation member as claimed inclaim 1 said outer member forming a chamber with said planar supportstructure when attached to said planar support structure, said chambercontaining said inner member seat.
 4. The vibration isolation member asclaimed in claim 1 wherein said inner member seat and said base planeare separated by a distance.
 5. The vibration isolation member asclaimed in claim 1 wherein the shroud is conical.
 6. The vibrationisolation member as claimed in claim 1 wherein the shroud is comprisedof a single wall.
 7. A combination comprising: (a) a planar supportstructure having a contiguous structure plane surface; (b) a suspendedbody located away from the support structure; and (c) a single resilientmember iso-elastic vibration isolation member joining the supportstructure and the suspended body to reduce the transmission of vibratorydisturbances between the suspended body and support structure, thevibration isolation member comprising; (i) an inner member comprising afrustoconical seat having an angled surface and an outer peripherydiameter D′; (ii) an outer member comprising a planar base and a shroudthat extends away from the planar base, the shroud extending to overlaythe inner member outer periphery diameter D′, said shroud having anangled segment with an inner surface, said angled segment inner surfaceoriented substantially parallel to said angled surface of saidfrustoconical seat, said shroud defining an inner periphery diameter D″,said inner periphery diameter D″ less than said outer periphery diameterD′, said outer member planar base joined to said planar supportstructure contiguous structure plane surface with said outer membershroud and said planar support structure contiguous structure planesurface comprising a chamber with the inner member seat contained insaid chamber; and (iii) consisting essentially of a single soleresilient member constrained between the shroud angled segment innersurface and the inner member frustoconical seat angled surface, saidsingle resilient member having a cross section, said single resilientmember bonded to said shroud angled segment inner surface and said innermember frustoconical seat angled surface, wherein said single resilientmember bonded to said shroud angled segment inner surface and said innermember frustoconical seat angled surface provides for iso-elasticdisplacement of said inner member in a radial direction and in an axialdirection from said outer member with said frustoconical seat outerperiphery diameter D′ providing an interference with said shroud innerperiphery diameter D″ to prevent a seperation of the vibration isolationmember in the event of a failure of said single resilient member whereinsaid single sole resilient member is the sole resilient member providingfor isolation between the suspended body and the support structure withsaid iso-elastic vibration isolation member providing a substantiallyequal dynamic stiffness in the radial direction and in the axialdirection for an applied load between the suspended body and the supportstructure.
 8. The combination as claimed in claim 7 wherein the innermember includes a cylindrical stem.
 9. The combination as claimed inclaim 7 wherein said inner member seat does not extend into said supportstructure plane surface.
 10. The combination as claimed in claim 9wherein the support structure plane surface and said inner member seatare separated by a distance.